my first post.....
so just to state m not nagato or uchiha fan boy m n edward elric fan

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nagato>itachi in power n ofcourse experience
itachi>nagato in intelligence and strategies
itachi has low stamina as stated by data book n data book is written by kishi.
nagato is uzumaki so very high stamina.
itaci might b a good ninjutsu user but nagato easily owns him on that
susano drain lot of itachi chakra and nagato has huge chakra reserves as seen against naruto....
and most imp thing kishi says things via manga....
for example itachi said he wud take kabuto n naruto has to take on tobi n sasuke...
he even said to naruto to not push himself....
so if he thought he could defeat nagato on his own he wud have said so .....
he asked for help that itself means that ho cudnt win alone.....
btw the order of development is byakugan then s then ms then ems then rinnegan so its not possible to put rinnegan in ocular genjutsu becuase it was the eye that made it ....
btw kabuto is a noob luk the way madara is using it the eye is still stilll same n nagato has more chakra (uzumaki)
nagato has so many summons and itachi has none and summons can change the game ....